MySQL & Navicat（四）一张图详解GROUP BY

GROUP BY的运行过程

GROUP BY的语法：

SELECT col_name, aggregate_function(col_name)......
FROM table_name
[WHERE col_name operator value]
GROUP BY col_name1,col_name2......
HAVING aggregate_function(column_name) operator value;

GROUP BY执行，依据指定列进行分组，相同值为一组，GROUP BY的值是同组数据共有的，之后合并所有数据，再进行输出的操作

举个例子:

SELECT 语文，数学
FROM 成绩表 GROUP BY 班级